Formation and drainage of aqueous humor following total iris removal and ciliary muscle disinsertion in the cynomolgus monkey.

Aqueous humor formation (AHF), uveoscleral flow (U), gross outflow facility (Cg), true facility of outflow from the anterior chamber (Ct1), true facility of outflow from anterior chamber into the general circulation (Ct2), and the pressure sensitivity of AHF (pseudofacility; Cps) were determined in cynomologus monkey eyes which had undergone total iris removal or iris removal followed by ciliary muscle disinsertion. AHF was in the normal range in iridectomized-only eyes. AHF was present but reduced in "disinserted" eyes. U was markedly reduced and similar in both types of eyes. Cps was normal and Cg, Ct1, and Ct2 were low in "disinserted" eyes. Cg, Ct1, and Ct2 were nearly equal in the "disinserted" eyes, indicating that gross facility consisted almost entirely of pressure-dependent flow from anterior chamber into the general circulation, presumably via the conventional drainage routes.     

Echothiophate-induced structural alterations in the anterior chamber angle of the cynomolgus monkey.

Four cynomolgus monkeys were treated topically twice daily in one eye with echothiophate iodide (PI) doses of 63, 75, or 250 micrograms per treatment for 7.7 weeks to 7 months. The opposite eyes of two monkeys received a control solution (diluent). The anterior ocular segments of all six eyes were studied by light and transmission electron microscopy during treatment. In the PI-treated eyes, the cribriform and outer corneoscleral meshwork were unusually dense. The trabecular meshwork was collapsed and the lamellae showed thickened basement membranes and thickened sheaths of elastic-like material. Most endothelial cells were enlarged and activated. Some contained many glycogen particles; others showed evidence of degeneration. The cribriform meshwork contained much more extracellular fine fibrillar material than normal, and the endothelium of the inner wall of Schlemm's canal was damaged. The PI-contracted ciliary muscle had a more rectangular shape than normally contracted muscles, and the inner edge extended so far anteriorly that in some areas it overlapped and occluded the trabecular meshwork. The muscle cells appeared damaged, and their basement membranes were thickened. The nonpigmented epithelial cells of the ciliary processes showed signs of degeneration, and within the pars plana some contained large, weakly osmiophilic inclusions. The basement membrane of the ciliary epithelium was thickened everywhere. The stromal vessels of the pars plana were dilated, and signs of inflammation were present. The sphincter iridis was damaged and there were iridocorneal adhesions. The 5 month diluent-treated eye demonstrated mild structural abnormalities in the meshwork.     

Scanning electron microscopy of ciliary muscle of monkey eye

The three-dimensional structure of the ciliary muscles of the cynomolgus monkey eye was studied by scanning electron microscopy after the treatment of the muscle in 8 N hydrochloric acid. The meridional muscle bundles in the outer part of the ciliary body were closely arranged and multilayered, extending in a straight anteroposterior direction from its anterior tips to the distal terminal. The anterior part of the muscle bundles consisting of compactly associated small muscle bundles appeared to have a smooth surface and formed a broad belt partially covered by fibrocytes. The anterior tips of the muscle bundles were divided into slender bundles which were connected to the trabecular sheets. The distal terminal part of the muscle bundles tapered markedly in thickness and split into fine bundles resembling a brush, showing a firm fixation in the surrounding stroma of the ciliary body. In the anterior part of the ciliary muscle, the muscle bundles internally situated divided into two branches forming a Y-shape in their extension in the straight anteroposterior direction. The divided branches merged with the branches from other muscles of the same kind and formed muscle sheets with a reticular pattern separated by the stroma of the ciliary body. These adjacent muscle bundles were arranged occasionally like parquetry work, indicating that the sheets appeared to consist of oblique muscles in the meridionally sectioned specimen. In the present study paired tips of V-shape in the anterior part of both the meridional and oblique muscles were not observed. Beneath the obliquely extending muscle bundles, circumferentially arranged muscle bundles were observed, but the interconnection with the other two groups of the muscle bundles was not demonstrated.     

Age changes in rhesus monkey ciliary muscle: light and electron microscopy

The ciliary muscle from 44 rhesus monkeys ranging in age from 137-day fetuses and a 3-week neonate to 35-year-old adults was studied by light and electron microscopy. In the fetuses and the neonate, the muscle cells appeared immature, and the muscle consisted mainly of longitudinally oriented fibers. By age 1 year, the muscle fibers were aggregated into bundles, and within each bundle the individual fibers were packed tightly together. In sagittal section, the muscle now exhibited longitudinal, reticular and circular portions. The individual muscle cells exhibited ultrastructural characteristics which set them apart from other smooth muscle cells. Age-related structural changes occurred in the ciliary muscle and intramuscular nerves, beginning at 6 years. These included increasing numbers of lysosomes, 'fingerprints', and the appearance of myelin figures within some nerve endings and nerve fibers. These alterations became more frequent and pronounced with age, and in elderly animals were seen in all regions of the muscle and around its entire circumference. Additionally, the elderly animals exhibited overt degeneration of some muscle cells and some myelinated nerve fibers. The time-course of these age-related structural neuromuscular alterations parallels the decline of functional accommodative amplitude (i.e. presbyopia) and of the ciliary muscle's configurational response to peripheral pharmacologic and central electrical stimulation. This suggests a pathophysiologic, albeit (given the relatively moderate overall abnormalities) not necessarily causal, relationship. An age-related increase in the number of pigmented cells between the ciliary muscle bundles also occurred, with the anterior longitudinal region being affected last. This might reflect an age-related decline in uveoscleral drainage of aqueous humor.     

The optically determined corneal and anterior chamber volumes of the cynomolgus monkey

We described an optical method of measuring corneal volume and employed the optical method of Johnson et al. for measuring the volume of the anterior chamber in cynomolgus monkey. In 12 normal monkey eyes, the corneal volume was found to be 40.4 +/- 2.3 microliter (mean +/- S.E.) and the anterior chamber volume was 101.8 +/- 4.2 microliter (mean +/- S.E.).     

Effect of repeated anterior chamber perfusion on aqueous flow in the cynomolgus monkey

No differences were found between fluorophotometrically determined aqueous flow rates in cynomolgus monkeys having vs not having undergone prior repeated anterior chamber perfusion. This suggests that: repeated perfusion does not produce a progressive decline in the rate of aqueous formation; and the repeatedly perfused monkey eye can be validly used in studies of aqueous formation.     

Long-term effects of Q-switched ruby laser on monkey anterior chamber angle

In an attempt to clarify whether pulsed lasers might be able to cause permanent fistulas from the anterior chamber to the interior of the canal of Schlemm, slightly suprathreshold, low energy, small diameter Q-switched ruby laser pulses were applied to the trabecular meshwork of nine eyes of six rhesus monkeys. Clinical examinations during the next 2 months disclosed no adverse effect on the cornea, iris, lens, or retina. There was transient mild inflammation in five eyes. Intraocular pressure was not changed significantly; the facility determined by perfusion of the anterior chambers at 2 months was normal. Light microscopy and scanning electron microscopy show localized trabecular lesions; some are slightly indented, but there is no persistent penetration to Schlemm's canal. Endothelial cells, confluent with those of the cornea, cover the inner (anterior chamber) surface of the lesions. Cross-sections through the center of a lesion show that trabecular meshwork and Schlemm's canal have been obliterated by the treatment and healing; these changes are similar to those previously seen after argon laser monkey trabecular treatment. In the untreated areas, between pulsed laser application sites, trabecular meshwork and Schlemm's canal are normal by light microscopic and scanning electron microscopic examination. Any effect on IOP from this particular type of pulsed laser treatment of the trabecular meshwork is probably not due to trabeculopuncture and flow of fluid through the fistula.     

Effect of repeated anterior chamber perfusion on intraocular pressure and total outflow facility in the cynomolgus monkey

Total outflow facility was determined by two-level constant pressure perfusion of the anterior chamber in surgically virgin, aniridic, and ciliary muscle disinserted cynomolgus monkey eyes 6 to 13 times at 1- to 2-month intervals over periods of 8 to 24 months. Facility decreased approximately 15 to 20% between consecutive thirds of the perfusion history, independent of eye type. The facility decreases were too large to be explained by decreased uveoscleral facility or pseudofacility, and were not mediated by the iris, ciliary muscle, or gonioscopically or ultrastructurally apparent chamber angle alterations. They most probably reflected functional alterations in the trabecular meshwork/inner wall of Schlemm's canal. Intraocular pressure as measured by applanation tonometry did not increase progressively, most probably due to a decreased rate of aqueous humor formation.     

激光周边虹膜切除术后前房及房角形态评价方法的研究进展

激光周边虹膜切除术（LPI）通过部分解除瞳孔阻滞,增宽周边前房角,降低眼压而成为青光眼治疗的重要手段之一。LPI术后前房角形态的检测参数是评价LPI治疗效果的主要指标。随着检测手段的进步,目前对LPI手术前后前房及房角形态的评价正在逐渐深入。已有的房角检查方法包括前房角镜、超声生物显微镜（UBM）、眼前节OCT（AS—OCT）以及Pentacam等,每种方法均可获得其各自的评价参数,但也存在一定限制。就LPI术后上述检查方法在评价前房及房角形态方面的应用价值进行总结,同时总结LPI术后前房和前房角结构的变化。     

Cytoskeleton and tissue origin in the anterior cynomolgus monkey eye

We studied cytoskeletal proteins and other markers for embryologic origin in the outflow pathways of the aqueous humor, cornea, sclera, and ciliary muscle of the cynomolgus monkey. The corneal endothelium and trabecular cells stained with markers for vimentin, smooth muscle cell α-actin, F-actin, spectrin, vinculin, and talin. The endothelium of Schlemm's canal stained with markers for vimentin, spectrin, and F-actin. These results suggest that trabecular cells are a kind of myofibroblast and support the belief that the endothelial cells of Schlemm's canal are vascular in origin. Fibrillary staining with antibodies to vimentin, spectrin, neurofilament protein, and glial acid fibrillary protein was observed along and between the ciliary muscle cells. Cells in the deep sclera adjacent to the supraciliary space stained with antibodies to smooth muscle α-actin, α-vinculin, talin, and desmin. These cells may anchor ciliary muscle cells into the sclera or may be developmental remnants of ciliary muscle cells. Leu 19 immunoreactivity was found in the corneal endothelium, in all trabecular cells, in ciliary muscle cells, and in keratocytes and fibroblasts in the superficial part of the cornea and sclera. All of these cells are therefore likely to express neural cell adhesion molecules indicating neuroectodermal origin.     

The fate of anterior chamber flurescein in the monkey eye. 1. The anterior chamber outflow pathways.

As defined by freeze-dry tissue techniques, there are two distinct routes by which fluorescein leaves the anterior chamber of the living rhesus monkey eye. I. The conventional pathway: Within five minutes of the initiation of fluorescein perfusion through the anterior chamber, the conventional pathway filled. Tracer passed through the trabecular meshwork into Schlemm's canal, and flowed back within scleral and episcleral venous derivatives to enter large veins in the extraocular muscles. II. The uveo-vortex pathway: Fluorescein rapidly moved into the iris stroma and into the anterior part of the ciliary body. The anterior chamber border of the ciliary body is little more than a sparse mesh from which fluorescein entered directly into the substance of the anterior ciliary muscle. Fluorescein penetrated blood vessels in the iris stroma and in the anterior ciliary body from where it could be traced posteriorly to the equatorial choroid and vortex veins. The specific sequential tissue distribution of fluorescein strongly supports the existence of a uveo-vortex pathway for aqueous outflow.     

Aqueous humor dynamics following total iridectomy in the cynomolgus monkey.

Twenty-two cynomolgus monkeys underwent unilateral total iridectomy in vivo. Several weeks to several months postoperatively, intraocular pressure (IOP) was determined bilaterally by manometry under pentobarbital anesthesia (15 monkeys), by a minified Goldmann applanation tonometer under CI-744 anesthesia (16 monkeys), and by a minified Draeger applanation tonometer under light phencyclidine catalepsia (4 monkeys). Mean IOP in aniridic eyes was about 0.3 mm Hg, or about 3%, lower than in opposite eyes. IOPs of aniridic and opposite eyes of the individual monkeys were highly correlated in all groups. In 11 monkeys, resting total outflow facility and the facility response to intravenous pilocarpine were determined 6 to 9 weeks postoperatively by two-level constant-pressure perfusion under pentobarbital anesthesia. There were no significant differences between mean resting facility, postpilocarpine facility, or facility response to pilocarpine of aniridic and opposite eyes. Resting facility, postpilocarpine facility, and facility response to pilocarpine in aniridic and opposite eyes of the individual monkeys were each highly correlated. Total iridectomy in the cynomolgus monkey apparently has little, if any, effect on IOP, outflow facility, or facility response to intravenous pilocarpine, and the iris plays little, if any, role in mediating the facility response to intravenous pilocarpine.